PROJECT SUMMARY/ABSTRACT Infections caused by Gram-negative bacterial pathogens are on the rise in hospital and non- hospital settings. Indeed 4 of the 6 ?ESKAPE? pathogens ? recently highlighted as responsible for the majority of hospital infections and being exceedingly difficult to treat ? are Gram-negatives. The development of new antibiotics is complicated by the fact that Gram-negative bacteria have a highly impenetrable membrane that confers significant intrinsic resistance to antibacterial agents. Although it is clear that novel antibiotics for Gram-negative infections are desperately needed, there has been minimal progress in this regard, and it has been over 50 years since a new class of drugs have been approved for Gram-negative ESKAPE pathogens. Why is this? A chief reason is that no rules or guidelines have been developed that enable the accurate prediction of compound accumulation in Gram-negatives, thus it has been difficult to convert Gram-positive-only drugs into broad-spectrum agents, and impossible to create large collections of compounds that are biased for Gram-negative accumulation. We have been working to define the physicochemical features of small molecules that allow them to accumulate in E. coli. For this work, we have been constructing a large set of value-added, complex organic compounds, and these have been indispensable to our discoveries to-date. This important synthetic work will be dramatically facilitate by the acquisition of the proposed benchtop mass spectrometer, allowing for the rapid analyses and thus enhanced throughput of chemical reactions, many of which are difficult to follow through standard means.